The present invention generally relates to a vehicle drive system and, more particularly, to a surface engaging propulsion mechanism for driving and steering a vehicle.
Self-propelled land-based vehicles, such as automotive vehicles and robots, typically employ a power unit, such as an internal combustion engine or electric motor, a drivetrain for transferring power to one or more drive axles, and a plurality of wheels for frictionally engaging a ground surface to propel the vehicle in a steered direction. Conventional wheeled vehicles include rotatable drive wheels that frictionally engage the ground and are used as the propulsion mechanism to drive and steer the vehicle in a desired direction. The wheels are actuated by the power driven axle to turn about the rotary drive axis, and the wheels are turned left and right within a steering range to control directivity of the vehicle. In most vehicles, a steered wheel has a limited range of angular movement.
Some vehicles employ independently rotatable drive wheels as the propulsion mechanisms to provide enhanced turning ability. For example, four wheel steering systems have been introduced which allow all four wheels on a passenger vehicle to be turned to steer the vehicle. Other examples of independently steered wheels are found on robotic vehicles which employ propulsion mechanisms commonly referred to as swerve or crab steering.
While conventional wheeled propulsion mechanisms are widely used on automotive vehicles and robots, there exists a number of shortcomings in some of these wheeled vehicle designs. The steering assembly mechanism required to turn the wheels typically requires numerous components. Additionally, the steering control systems that are generally required to turn the wheels are complex and generally require many sensors and a great amount of software development. Thus, sophisticated steered wheel systems are generally expensive. Further, conventional steered wheel propulsion mechanisms generally experience a time delay to turn the wheels toward the path of the desired direction, due to the fact that the wheels may be turned throughout a wide turning radius.
It is therefore desirable to provide for a propulsion mechanism for driving a ground operated vehicle, which offers reduced time to steer the vehicle, reduced components, and reduced cost. It is further desirable to provide for such a propulsion mechanism which may be employed on any of a number of mobile vehicles.
In accordance with the teachings of the present invention, a propulsion mechanism is provided for driving a vehicle having a frame and a socket provided in the frame. According to one aspect of the present invention, the propulsion mechanism includes a spherical ball disposed within the socket and adapted to frictionally engage a surface. A first powered drive member is frictionally engaged with the spherical ball and is powered to rotate the spherical ball to propel the vehicle. A second powered drive member is frictionally engaged with the spherical ball and is powered to rotate the spherical ball to propel the vehicle. The first powered drive member drives the spherical ball in a first axis and the second powered drive member drives the spherical ball in a second axis.
According to another aspect of the present invention, the propulsion mechanism includes a spherical ball disposed in the socket of the frame, and a friction reducing load member disposed between the spherical ball and the frame for allowing the spherical ball to rotate relative to the frame. The propulsion mechanism further includes a powered drive member frictionally engaged with the spherical ball. The drive member is powered to rotate the spherical ball to drive the vehicle.
Accordingly, the propulsion mechanism of the present invention advantageously drives and steers a vehicle by employing a spherical ball frictionally engaged by drive members. According to a further aspect, the first and second drive members are controllably actuated so as to provide controlled steering of the vehicle in any of a number of directions.
These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.